Regulation of metabolism in the animal involves the interaction of hormonal influences on the mobilization and utilization of protein, fats and carbohydrates. The ultimate effect of a given hormone may be moderated by other hormones or metabolic events evoked by the hormone. The overall aim of this study is to determine the metabolic effects of the various hormones, investigate the hormonal interactions on the metabolic events and finally to examine how the metabolic alterations moderate responses to the hormones. Tracer amounts of radioactive glucose, palmitate and glycerol are used to measure the rates of production and utilization of the respective metabolic fuels in trained dogs. Concomitantly, plasma levels of insulin, glucagon, cortisol and growth hormone are also determined. These measurements will be made under altered experimental conditions including fasting, high fat and high carbohydrate diet, during reduction of lipolysis (by tetrazole), during specific stimulation of growth hormone secretion (by clonidine), and inhibition of glucagon secretion (by somatostatin along with insulin). The role of sympathetic nervous system will be examined using alpha and beta adrenergic blocking agents. The effect of graded insulin deficiency will be evaluated by using appropriate doses of streptozotocin.